No team has won the World Series in back-to-back seasons this century, and while that sounds impressive, the Astros will tell you it means absolutely nothing. They're probably right about that, especially given the fact that every baseball season has its own unique set of dynamics.
That said, the history is compelling. In the past 39 seasons, it has happened just twice: The Yankees won three straight championships in from 1998 to 2000; and the Blue Jays won in 1992 and '93.
When you factor those numbers into the game's landscape of parity and how every season postseason games typically are decided by thin margins and crazy moments, Houston's challenge should not be underestimated.
On the other hand, there's a case to be made for the team with the most talent winning the World Series. That's a good starting point. With the Astros preparing to defend their championship, let's take a look at both sides of the debate.
First, let's examine five reasons the Astros will repeat.
1. They're better
Justin Verlander and Gerrit Cole -- Opening Day starters for the Tigers and Pirates, respectively, last season -- have been added to Houston's rotation since Aug, 31. Charlie Morton and Brad Peacock are coming off transformative and confidence-building seasons. General manager Jeff Luhnow strengthened his bullpen with the addition of free agents Joe Smith and Hector Rondon. And there's still baseball's deepest and best lineup.
2. George Springerwill dance in the dugout again
When the Astros were running away with the American League West at midseason, manager A.J. Hinch was asked how his team could maintain its competitive edge. "Just watch us play," he said. Houston played with energy and joy last season. The Astros celebrated victories and shrugged off losses. They came from behind to win 43 times and won eight times when trailing in the eighth or ninth inning. To watch Springer -- and others -- is to understand their competitive fire is unlikely to lower.
3. Personal goals count, too
Most of the Astros' core players still have plenty to play for. Jose Altuve, Dallas Keuchel, Carlos Correa and Springer have not had a crack at free agency and the kind of life-changing money that every player strives to make. All of them are still trying to put themselves in that position. As for Verlander, it's about winning again, while putting the finishing touches on his Hall of Fame resume.

4. That bullpen could be really good
OK, it wasn't a good postseason for the bullpen. Funny thing is, with about six weeks left in the regular season, they thought they would take a dominant group into the postseason. And then closer Ken Giles and All-Star setup men Will Harris (2016) and Chris Devenski ('17) hit a wall simultaneously. All of them return with great stuff and plenty to prove. Besides that, Peacock probably will start the season in the bullpen, along with newcomers Smith and Rondon.
5. Hinch and Luhnow
Hinch and Luhnow might be the prototypes of what almost every team is looking for in a manager and general manager. Hinch's spring task will be getting his players to turn the page on a magical season and begin the hard work of trying to win again. Given his knack for saying and doing precisely the right thing, again and again, he'll probably pass this test with flying colors. Luhnow's job is to monitor the current roster and to be ready to adjust again. Few GMs have done their jobs better since he arrived in Houston in December 2011.
On the other hand, the Astros' rally might not win again. At least a dozen teams believe they're good enough to win a championship in 2018, and the AL is better overall.
While this list is considerably shorter and decidedly less convincing, let's look at five reasons Houston might not win the World Series in 2018.
1. The competition
Look at the AL teams that have gotten better. The Yankees, who were one game short of going to the World Series, added the National League MVP Award winner (Giancarlo Stanton). The Angels made additions up and down the roster, including outfielder/DH/pitcher Shohei Ohtani, baseball's most intriguing player in 2018. The Indians are still really good. The Red Sox, Blue Jays, Mariners and Twins could also be in the mix. The Dodgers, Cubs, Nationals, etc., lurk over the horizon as formidable World Series opponents. Gulp.
2. Injuries
Lance McCullers, Correa, Keuchel and Springer all spent time on the disabled list in 2017, and that's a reminder that even the deepest teams are tested in all sorts of ways. The Astros have depth up and down their roster, but they're unlikely to win without their core guys being at their best.
3. Luck
The Astros came from behind to win three of their four World Series victories. Of Houston's 11 postseason wins, five were decided by one run. The Astros scored the winning run in the ninth inning or later three times. Some of those games came down to one pitch or one moment, the thinnest of margins.
4. Human nature
Does winning a World Series whet a team's appetite for winning again, or does it inevitably remove some of the drive from the psyche? The Astros do not believe complacency will be a problem, but this surely is among the reasons so few teams go back to back.
5. No secrets
The Astros probably once had an advantage in terms of scouting reports, pitch usage and the dozens of ways they use the massive amount of data they collect. But the Yankees now have a bigger analytics department, and most other teams have tried to emulate Houston's formula. When so many games are so close, little things could add up.